Mine's been living in a dry north facing flower bed and it does have 1 flower spike each year. I think you might need to let it do its own thing for a while (although it will take over). See if this improves it.

A light feeding--perhaps with Grow More?--might also stimulate bloom. Also double check the sun exposure: it doesn't need direct sun to bloom, but it does need bright indirect light. Too deep under a dense tree will stop the bloom.

If you try to remove it, the smallest piece of root will regrow. The only way really to get rid of it is to dig out as much root as you can, and then treat any new shoots with a systemic weedkiller as soon as they appear. It will take several applications, but you will win eventually.

I've been digging mine out annually for several years now...

Thanks for your replies. I noticed on GW that the new border that MD was creating had a couple of clumps of it. I will leave it alone for a while and see what happens. It is on a west facing border. I'm just a bit concerned that it might take over so will try and keep it controlled .

I've found it helps if you deadhead it to prevent self-sown seedlings from adding to the problem.